[1] Field of the Invention
The present invention relates to a gate valve connected to a processing chamber of a semiconductor manufacturing apparatus or the like to open and close a communicating channel communicating with the processing chamber such as a fluid channel or a goods transfer channel.
[2] Description of the Related Art
In Patent Literatures Japanese Unexamined Patent Application Publication No. 2002-195424 and Japanese Unexamined Patent Application Publication No. 2005-291221, a gate valve connected to a processing chamber of a semiconductor manufacturing apparatus or the like and configured to open and close a communicating channel communicating with the processing chamber with a valve plate provided in the interior of the valve box is disclosed. In such a gate valve, since a seal member of the valve plate is subject to damage due to a corrosive fluid such as process gas or the like flowing in the communicating channel, replacement of the seal member with a new one is required as needed.
In order to facilitate the replacement of the seal member, in the gate valve described in Patent Literatures JP No. 2002-195424A and JP No. 2005-291221A, an upper end of the valve box, that is, a surface of the valve box on the side opposite from a side where a valve rod for causing the valve plate to open and close is introduced is opened to allow the valve plate to be taken out therethrough, is provided with a plate-shaped lid member for allowing the opening to be opened and closed thereby. In addition, by opening the lid member, the valve plate at a tip end of the valve rod is allowed to be demounted from the side of the opening, whereby the valve plate can be taken out easily from the valve box.
However, the mounting and demounting structure of the valve plate with respect to the valve rod is limited to a range which allows easy mounting and demounting operation through the opening at the upper end of the valve box. Therefore, it is difficult to mount the valve plate stably to the tip end of the valve rod, or there are various problems as described below.
For example, in the gate valve disclosed in Patent Literature JP No. 2002-195424A, a projecting portion of a leaf spring member mounted on the valve rod is engaged with an opening portion of the valve plate, and the valve plate is fastened to the valve rod by a resilient force of the leaf spring member (FIG. 4 and FIG. 5 in the same Literature JP No. 2002-195424A), or an inclined surface is provided on a mounting potion at the tip end of the valve rod to be mounted in the hole portion of the valve plate and a wedge member to be engaged with the inclined surface and an inner side surface of the valve plate is fixed to the tip end of the valve rod by tightening a screw member (FIG. 8 and FIG. 9 of the same Literature JP No. 2002-195424A).
In the configuration shown in FIG. 4 and FIG. 5 of the above-described Literature, mounting and demounting of the valve plate is easy. In contrast, since the fixation is achieved by the resilient force of the leaf spring, the leaf spring member may be deformed and cause dust when the seal member (O-ring) of the valve plate is secured to a valve seat or the valve plate may come apart from the valve rod, while in the configuration shown in FIG. 8 and FIG. 9 of the above-described literature, since the fixation is achieved only at the tip end of the valve rod, the valve plate might be mounted in an inclined position, so that the valve plate cannot necessarily be fixed stably so as to oppose accurately with respect to the communicating channel of the valve box.
Furthermore, although the gate valve of the above-described Patent Literature JP No. 2005-291221A includes a radial bearing portion and a rotational angle limiting portion at a connecting portion at the tip end of the valve rod to be inserted into a plug receipt of the valve plate, and is configured in such a manner that the radial bearing portion described above allows the valve plate to rotate with respect to the valve rod and to be deformed so as to follow the shape of a valve seat when the valve plate is pressed against the valve seat, and the rotational angle limiting portion limits the rotation allowed in the radial bearing portion to fall within a predetermined angular range. This configuration, however, cannot fix the valve plate stably so as to oppose accurately with respect to the communicating channel of the valve box.